1. Field of the Invention
The present invention relates to a linear guide apparatus used in various machines of a manufacturing apparatus, a working machine, a measuring instrument and the like.
2. Description of the Related Art
A linear guide apparatus is an apparatus for linearly guiding an object to be guided, not illustrated, fixed to a slider as disclosed in, for example, JP-A-5-280537. As shown by FIG. 14, a linear guide apparatus is provided with a guide rail 1 and a slider. The slider 2 has a section substantially in a U-like shape riding over the guide rail 1 and is attached with the object to be guided. As shown by FIG. 8A, guide rail side trace faces 3, 4 are formed at side faces of the guide rail 1, and slider side track faces 5, 6 are formed at inner peripheral faces of leg portions of the slider 2. A load portion track path is formed by arranging the guide rail side trace faces 3, 4 and the slider side track faces 5, 6 opposedly to each other. Circulation passages are formed at end caps 50 and at inside of the slider 2. Both of the load portion track path and the circulation passages form an endless circulation passage for rollers. A plurality of cylindrical rollers are arranged at inside of the endless circulation passage and the plurality of cylindrical rollers are rolled at inside of the endless circulation passage in accordance with relative movement of the slider 2. Further, as described above, the linear guide apparatus is used in various machines of a semiconductor manufacturing apparatus, a precision working machine, a precision measuring instrument and the like.
Here, as shown by FIG. 8B, in the guide rail side track faces 3, 4 and the slider side trace faces 5, 6 opposed to each other, the track faces of the guide rail 1 and the slider 2 are worked to finish such that the two track faces constitute faces in parallel with each other in view from an axial direction of the guide rail 1 in a no load state in which the rollers are not interposed thereto.
The linear guide apparatus in which rolling elements are the cylindrical rollers is frequently used for use needing a high rigidity particularly in a machine tool or the like. Therefore, in order to achieve a sufficient rigidity, the rollers are interposed between the track faces opposed to each other by being applied with a sufficient preload.
However, by the preload, the slider 2 is elastically deformed to open left and right leg portions 2A. FIG. 5 shows a result of calculating a state of the elastic deformation by an FEM analysis. As shown by FIG. 5B, left and right sides of a horizontal portion 2B are warped to an upper side and deformed in a shape of opening a total of the left and right leg portions 2A. Therefore, in a state of bringing the linear guide into a usable state by interposing the cylindrical rollers, the slider side track faces 5, 6 are inclined by a predetermined angle relative to the guide rail side track faces 3, 4.
A degree of the inclination differs by loading an external load from the object to be guided or the like. FIG. 5C shows a result in consideration of the external load.
According to the linear guide apparatus of the related art, in a state of use interposing the rollers, the pairs of track faces opposed to each other are not in parallel with each other and therefore, contact pressures between the rollers and the respective track faces are not distributed uniformly but distributed unevenly and the pressures differ depending on contact positions. FIG. 9 shows a result of calculating a state of distributing the contact pressure between the roller and the track in a direction of a roller axis. Running life of a total of the linear guide apparatus is significantly dependent on running life of a portion of the roller at which the contact pressure is the largest. That is, when there is a deviation in the distribution of the contact pressure as shown by FIG. 9, a face pressure of a portion of the roller is abnormally increased to thereby shorten the life of the total of the linear guide apparatus. Further, when the roller is brought into an uneven contact state in this way, there is a concern of effecting an influence on an attitude of the rolling roller.
Meanwhile, in order to reduce an inclination between the track faces by such a deformation of the members, there is conceivable a method of increasing a rigidity of the members. However, for increasing the rigidity, it is necessary to increase a dimension of the member, which hinders compact formation of the apparatus.